1. Field of the Invention
The present invention relates to a film speed setting device for use in a photographic camera.
2. Description of the Prior Art
There is already proposed, for example in the U.S. Pat. Nos. 4,024,557 and 4,173,401, a system in which a digital code or indicia representing the film speed is formed on the film cartridge or magazine and is automatically detected by a detecting device provided in the camera. Such system is extremely effective in preventing the problem of erroneous setting of the film speed through an error of the operator. Also the U.S. Pat. No. 4,200,371 discloses a camera in which the film speed setting dial has an automatic setting position and is to be set at this position when a film cartridge having the digital code or indicia is used. More specifically, the system of said prior art is capable of automatically setting the film speed when a film cartridge bearing the digital code is loaded, or giving a suitable alarm to instruct the operator to move said film speed setting dial to a suitable manual position and simultaneously locking the shutter release button in case a film cartridge lacking the digital code is loaded while the setting dial is placed at the automatic film speed setting position. It is also proposed to give an alarm and to lock the shutter release button for preventing an error, in case a film cartridge with the digital code for example for a film speed of ISO 400 is loaded while the setting dial is placed at a manual position for example for a film speed of ISO 100.
However certain operators may wish to obtain a particular effect in the modified graininess by a push development of a film of ISO 100 to a speed of ISO 400, and the locking of the shutter release button is a rather unwelcome measure for such operators.